The present invention relates to a deflecting yoke for electromagnetic deflection type cathode-ray tubes (hereinafter referred to as CRT) used in televisions and a variety of displays and a method for manufacturing it, and more particularly it relates to a deflecting yoke which is excellent in temperature stability and which is high in magnetic flux density, and a method for easily manufacturing it.
Heretofore, as materials for the deflecting yokes for the CRT, ferrite cores have often been employed from the viewpoint of frequencies used for deflection (e.g., Japanese Patent Publication No. 31557/1977 and Japanese Provisional Patent Publications Nos. 152298/1975 and 145996/1979).
However, in the usual ferrite core, a change in its magnetic properties owing to a temperature is as great as 20% or more even in the range of usable temperatures. Therefore, in the case that the ferrite core is utilized as the deflecting yoke for the CRT, its magnetic properties such as magnetic flux density disadvantageously will change under the influence of a variation of an ambient temperature, a temperature rise around the deflecting yoke during the operation of an instrument carrying the CRT, a temperature rise of a deflecting coil or the deflecting yoke itself due to a loss of them, and the like. For this reason, when the ferrite core is used as the deflecting yoke for the CRT, suitable measures will have to be taken to eliminate the above-mentioned disadvantage also on the side of the used instrument, so that it will be derived the problem that the instrument will become intricate in structure on the whole.
On the other hand, as a material having excellent temperature properties, so-called dust cores are known which may be manufactured, for example, by binding particles of a carbonyl iron powder with a phenolic resin or the like (e.g., Japanese Pat. Nos. 88779 and 112235).
These dust cores are excellent in temperature properties but their magnetic flux densities are 0.1 to 0.2 tesla (T) with respect to an excitation force of 10000 A/m, which value is smaller than that of the ferrite. If an attempt is made to provide necessary magnetic properties, the yoke will have to be enlarged in size, but at this time, there will be required more deflecting electric power than in the case of the ferrite. In consequence, these dust cores have scarcely been put into practice.
In view of the situations, Japanese Provisional Patent Publication No. 123141/1984 discloses a deflecting yoke comprising an iron powder or an iron alloy powder and a resin, by which the above-mentioned problems can be overcome.
Further, if the temperature rise in a yoke can be depressed than that of the deflecting yoke as described in Japanese Provisional Patent Publication No. 123141/1984 without impairing the advantages thereof, it will be considered that a deflecting yoke having high magnetic flux density and low temperature rise can be obtained.
When the temperature rise in a yoke was depressed by adding a third component to starting materials of the yoke, a fluidity of the starting materials would be lowered.